1. Field of the Invention
This invention relates to high cold-forging electromagnetic stainless steels having an excellent cold forging property and good soft magnetic properties and corrosion resistance, which are particularly suitable as a valve housing material, a valve sleeve or a valve core material of an electronically controlled fuel injection system for automobiles.
2. Description of the Related Art
The electronically controlled fuel injection system for automobile is widely used in many automotive vehicles with rapid advancement of car electronics. As a material for parts constituting this system, 13Cr-1Si-Al ferritic stainless steels are practically and frequently used from a viewpoint of demands on corrosion resistance and soft magnetic properties.
In order to reduce the cost for working these parts, the working is switching over from cutting work to cold forging work, and particularly it is directed to all work these parts through the cold forging.
Under such a circumstance, it has hitherto been attempted to improve the cold forging property by reducing amounts of (C+N) in the above 13Cr-1Si-Al alloy steel.
However, the shape of the parts used in the electronically controlled fuel injection system is very complicated, so that the effect by the reduction of (C+N) amount is still insufficient even in the existing 13Cr-1Si-Al alloy steel.
On the other hand, the use of alcohol fuel is earnestly examined with the diversification of automobile fuel. In this case, the occurrence of corrosion accompanied with the formation of acetic acid or formic acid by oxidation of alcohol is feared. Furthermore, it is required to have a corrosion resistance to chloride through snow melting agent used in winter season.
Moreover, the material used for the electronically controlled fuel injection system is particularly required to have soft magnetic properties. The improvement of such magnetic properties directly connects to the improvement of characteristics in the electronically controlled fuel injection system.
As mentioned above, the properties required in the material used for the electronically controlled fuel injection system extend over a wide area and interrelate to each other. In many cases, these properties are conflicting with each other.